KRASNAYA POLYANA, Russia -- Again, there was nothing in front of Lindsey Jacobellis but open snow, a finish line and a mountain of possibility. She was in the lead, a pack of women chasing from behind with little hope of catching the most accomplished female snowboard-cross rider in history.

In 2006, at the Olympics in Turin, Roxbury native Jacobellis had a similarly wide gap in the final when, after launching off the second-to-last jump, she grabbed her board with her hand and twisted sideways, trying to punctuate her run with panache. She crash landed and was passed, turning gold into silver, the most heartbreaking feat of Olympic metallurgy.

This time, it was the semifinals, and it was not a showy midair move that brought Jacobellis to earth.

It was a couple of rollers, gentle but devious little humps near the bottom of the course, just above the final jump. Jacobellis came around a tight corner, rose off one roller, landed awkwardly on another, and spun to the ground.

She never reached the finish line, which meant she did not realize the elusive dream of turning her dominating career into Olympic gold. Four years ago in Vancouver, again the gold medal favorite, Jacobellis lost in the semifinals, too. That time, in a crowd, she nearly landed on another competitor's snowboard, wobbled off balance and went out of bounds.

"I don't think it has to do with the Olympics," Jacobellis said. "It's just on a fluke of when things work out for me and when they don't."

An eight-time winner of the event at the Winter X Games, Jacobellis, 28, was placed in the "small final," a consolation run. She won that six-person contest, officially giving her a seventh-place finish at the Olympics.

"I was really happy with how the course was coming together for me," Jacobellis said glumly, but without the obvious signs of heartache. "I wasn't scared. There were a lot of girls who were scared, and not really putting it together. It just didn't work out. I don't know how else to say it."

It was Eva Samkova of the Czech Republic who dominated the event, from timed qualifications to the final race, to win the gold medal. Dominique Maltais of Canada earned silver, and Chloe Trespeuch of France captured bronze. As they crossed the finish line in a line, each raised her arms triumphantly, pleased with the result, if not simply happy to survive standing up.

"I couldn't imagine this," said Samkova, who had painted a handlebar mustache above her lip in the national colors of red, white and blue.

Faye Gulini of the United States finished fourth, an outcome charged with mixed emotions.

"I'm happy with fourth," she said, pleasantly. "But it is the Olympics. Being on the podium would have been nice."

The topic turned to Jacobellis, as it often does at these events. Gulini quickly came to the defense of her fallen teammate.

"People don't understand how much pressure is put on her," she said. "It breaks my heart, because I think it takes the fun out of it for her. Just this event. She loves the sport. She's a phenomenal snowboarder. But it's in her head. With that much pressure on you -- I've never had that kind of pressure on me -- but I know that it just breaks her, as an athlete."

She added: "Maybe it was just a fluke mistake. But it's a bummer. She deserves more."

The course of big jumps, knee-bending rollers and banked corners took its toll on the athletes from the beginning. Two of the first six women to take the course in timed qualifiers, medal contender Helene Olafsen of Norway and Jacqueline Hernandez of the United States, were hauled down the course on sleds after nasty falls.

Olafsen, who finished fourth at the 2010 Vancouver Games, appeared to hurt her knee. Hernandez flew off a jump and landed sideways on her board, toppling onto her back and hitting her head. She was diagnosed with a concussion and released in time to watch the end of the event.

The women's snowboard cross arrived ripe in story lines. Torah Bright of Australia competed in her third snowboard event, after slopestyle and halfpipe, in which she won a silver medal. In snowboard cross, though, she was quietly ousted in the quarterfinals.

And Belle Brockhoff, another Australian, publicly announced in August that she was gay in the wake of news about Russia's antigay legislation. Brockhoff, one of seven known gay athletes at the games (all women), said she would have some words for President Vladimir Putin of Russia.

"After I compete, I'm willing to rip on his" backside, she said. "I'm not happy and there's a bunch of other Olympians who are not happy, either."

Brockhoff missed out on the final, and finished behind Jacobellis in the small final, earning eighth. Afterward, she offered few words on the subject of gay rights, suggesting that social media might be a better format for her views.

That kept most of the attention on Samkova, the winner, and Jacobellis, the upended favorite. Samkova dominated her races the way that Jacobellis, in a different semifinal, was dominating hers.

Jacobellis carried more speed around a hard left-hand bend in the semifinal than she had in the quarterfinal. She hit the first roller of a short straightaway and flew past where she intended to land. She came down awkwardly on an uphill slope that faced the midday sun -- "kind of like landing in mashed potatoes," Jacobellis said -- and slid into the course's final turn, a right-hander that led to a drop-off and the final jump.

As it was eight years ago, it was a self-inflicted mistake in a manic, unpredictable sport of collisions and wipeouts. As she was eight years ago, Jacobellis was philosophical about the result.

"There's worse things in life than not winning," she said. "A lot worse. Of course, it's very unfortunate that this didn't work out for me, and I trained very hard for this moment. It doesn't come together, for who knows what reasons."